1. Field of the Invention
The present invention relates to an intake system for a multi-cylinder engine, in which an intake air inlet is provided in an intake air-dispensing box to lead to an intake passage in a throttle body; the inside of the intake air-dispensing box is divided by a partition wall into first and second dispensing chambers communicating with the intake air inlet; first and second intake branch pipes opening into the first and second dispensing chambers and leading to intake ports in first and second banks of the engine are connected to the intake air-dispensing box; and an on-off valve is mounted in the partition wall and capable of permitting the first and second dispensing chambers to be put into and out of communication with each other, so that the air-charging characteristic can be changed by opening and closing the on-off valve depending on the operational state of the engine, thereby maintaining a high outputting performance in a wider operational range from a low speed to a high speed.
2. Description of the Related Art
A conventional intake system for a multi-cylinder engine is already known, as disclosed, for example, in Japanese Patent Application Laid-open No. 9-88746.
In the intake system disclosed in the above Japanese Patent Application Laid-open No. 9-88746, the partition wall supporting the on-off valve and having a valve bore opened and closed by the on-off valve is interposed between a dispensing box body and an intake manifold. Therefore, to carry out the maintenance of the on-off valve, a troublesome operation of disassembling the dispensing box body and the intake manifold from each other is required, so that the maintenance property is not good.
Accordingly, it is an object of the present invention to provide an intake system of the above-described type for a multi-cylinder engine, wherein the maintenance of the on-off valve can be carried out only by removing a lid mounted outside the intake air-dispensing box from the box, leading to a good maintenance property.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided an intake system for a multi-cylinder engine, in which an intake air inlet is provided in an intake air-dispensing box to lead to an intake passage in a throttle body; the inside of the intake air-dispensing box is divided by a partition wall into first and second dispensing chambers communicating with the intake air inlet; first and second intake branch pipes opening into the first and second dispensing chambers respectively and leading to intake ports in first and second banks of the engine respectively are connected to the intake air-dispensing box; and an on-off valve capable of permitting the first and second dispensing chambers to be put into and out of communication with each other is mounted in the partition wall; wherein the intake air-dispensing box is comprised of a dispensing box body which includes the intake air inlet, the first and second intake branch pipes and one of halves of the partition wall and which has an opening provided in its outer wall opposite from the first and second intake branch pipes to extend between the first and second dispensing chambers, and a lid detachably coupled to the dispensing box body to close the opening and having the other half of the partition wall, the lid being made of a light alloy by casting, and a valve bore permitting the first and second dispensing chambers to be put into communication with each other and bearing bores for supporting a valve shaft of the on-off valve for opening and closing the valve bore are defined in the other half of the partition wall.
With the first feature, a single assembly is formed by the lid and the on-off valve and hence, the maintenance of the on-off valve and the members around the on-off valve can be carried out easily by removing the lid from the dispensing box body, thereby contributing to an enhancement in maintenance property.
Moreover, the lid made of the light alloy by casting is small in size and simple in shape, as compared with the dispensing box body integral with the intake branch pipes and hence, can be precisely formed by casting such as high-pressure die-casting. Therefore, the post-processing of the valve bore is not required and moreover, the lid having such a high quality that deformation cannot be generated therein even due to a change in the surrounding temperature, can be produced easily, and the good opening and closing operation of the on-off valve supported on the lid can be always ensured irrespective of the change in the surrounding temperature.
According to a second aspect and feature of the present invention, in addition to the first feature, the other half of the partition wall is divided into a main partition other-half body and a partition piece so that the valve bore is divided along the bearing bores into halves, the partition piece being bolted to the main partition other-half body.
With the second feature, when the main partition other-half body and the partition piece of the partition wall are produced by casting, the halves of the valve bore included respectively in the main partition other-half body and the partition piece can be die-formed simply, and a troublesome processing for the valve bore is not required after the casting, leading to an enhancement in productivity.
According to a third aspect and feature of the present invention, there is provided an intake system for a V-type engine for an outboard engine system, which is disposed with a crankshaft placed vertically and with heads of left and right banks directed rearwards and which is covered with an engine hood; wherein an intake air inlet is provided in vertically one side of a longitudinally flat intake air-dispensing box disposed between the left and right banks and a rear wall of the engine hood so that the intake air inlet leads to an intake passage in a throttle body; the inside of the intake air-dispensing box is divided by a partition wall into left and right dispensing chambers communicating the intake air inlet and extending vertically; an on-off valve capable of permitting the left and right dispensing chambers to be put into and out of communication with each other is mounted in the partition wall; left and right intake branch pipes opening into the left and right dispensing chambers respectively and leading to intake ports in the left and right banks respectively are connected to a front wall of the intake air-dispensing box; the intake air-dispensing box is comprised of a dispensing box body which includes the intake air inlet, the left and right intake branch pipes and one of halves of the partition wall and which has an opening provided in its outer wall opposite from the left and right intake branch pipes to extend between the left and right dispensing chambers, and a lid which is made of a light alloy by casting and detachably coupled to the dispensing box body to close the opening and which has the other half of the partition wall; the on-off valve is mounted to a valve shaft rotatably supported in the other half and extending vertically; an operating lever is secured to an outer end of the valve shaft protruding toward the vertically other end of the intake air-dispensing box; and an actuator for turning the operating lever to open and close the on-off valve is mounted at the other end of the intake air-dispensing box and accommodated within an area of a vertically projected view of the intake air-dispensing box.
With the third feature, resonant supercharging intake systems corresponding to low-speed and high-speed operational ranges of the engine are formed by opening and closing of the on-off valve, whereby a high outputting performance can be exhibited in a wider operational range. Moreover, the longitudinally flat intake air-dispensing box is disposed in proximity to the heads of the left and right banks of the engine and hence, can be disposed in a narrow space between the engine and the rear wall of the engine hood. Thus, it is possible to provide an enhancement in a space efficiency of the engine room and to suppress an increase in size of the engine hood.
The single assembly is constituted by the lid and the one-off valve and hence, the maintenance of the on-off valve and members around the latter can be carried out easily by removing the lid from the dispensing box body, thereby contributing to an enhancement in maintenance property.
Moreover, the lid made of the light alloy is small in size and simple in shape, as compared with the dispensing box body integral with the intake branch pipes and hence, can be precisely formed by casting such as high-pressure die-casting. Therefore, the post-processing of the valve bore is not required and moreover, a lid having a high rigidity and such a high quality that deformation cannot be generated even due to a change in the surrounding temperature, can be produced easily, and the good opening and closing operation of the on-off valve supported in the lid can be always ensured irrespectively of the change in the surrounding temperature.
Further, the position of the actuator for opening and closing the on-off valve can be determined freely around the valve shaft by selection of the position of operating lever coupled to the valve shaft of the on-off valve and hence, it is easy to accommodate the actuator within an area of a vertically projected view of the intake air-dispensing box. Thus, it is possible to simply avoid the interference of the actuator with the rear wall of the engine hood disposed in proximity to the rear surface of the intake air-dispensing box. Moreover, the intake air inlet and the actuator are disposed at vertically opposite ends of the intake air-dispensing box and hence, it is also possible to avoid the interference of the intake air inlet and the actuator with each other to provide the compactness of the intake system.
According to a fourth aspect and feature of the present invention, in addition to the third feature, the other half of the partition wall is divided into a main partition other-half body and a partition piece so that the valve bore is divided along the bearing bores into halves, the partition piece being bolted to the main partition other-half body.
With the fourth feature, when the main partition other-half body and the partition piece of the partition wall are produced by casting, the halves of the valve bore included respectively in the main partition other-half body and the partition piece can be die-formed simply, and a troublesome processing for the valve bore is not required after the casting, leading to an enhancement in productivity.
According to a fifth aspect and feature of the present invention, in addition to the third or fourth feature, a recess for accommodating the actuator is defined in the vertically other end face of the intake air-dispensing box.
With the fifth feature, the actuator of a relatively large size can be placed in the narrow engine room without interfering with the intake air-dispensing box and the engine hood.
According to a sixth aspect and feature of the present invention, there is provided an intake system for a multi-cylinder engine, in which an intake air inlet is provided in one end of an intake air-dispensing box disposed on one side of an engine having first and second banks so that it leads to an intake passage in a throttle body; the inside of the intake air-dispensing box is divided by a partition wall into first and second dispensing chambers communicating with the intake air inlet; an on-off valve capable of permitting the first and second dispensing chambers to be put into and out of communication with each other is mounted in the partition wall; and first and second intake branch pipes opening into the first and second dispensing chambers respectively and leading to intake ports in the first and second banks respectively are connected to the intake air-dispensing box; wherein the intake air-dispensing box is comprised of a dispensing box body which includes the intake air inlet, the first and second intake branch pipes and one of halves of the partition wall and which has an opening provided in its outer wall opposite from the first and second intake branch pipes to extend between the first and second dispensing chambers, and a lid made of a light alloy by casting and having the other half of the partition wall, and a valve bore permitting the first and second dispensing chambers to be put into communication with each other and bearing bores for supporting a valve shaft of the on-off valve for opening and closing the valve bore are defined in the other half of the partition wall; the bearing bores are made in the other half of the partition wall by drilling from a side opposite from the intake air inlet and disposed offset from a lengthwise central portion of the partition wall to a side of the partition wall opposite from the intake air inlet; and an actuator connected to the valve shaft to open and close the on-off valve is mounted at the other end of the intake air-dispensing box opposite from the intake air inlet.
The first and second banks correspond to left and right banks in an embodiment of the present invention which will be described hereinafter.
With the sixth feature, a single assembly is formed by the lid and the on-off valve and hence, the maintenance of the on-off valve and the members around the on-off valve can be carried out easily by removing the lid from the dispensing box body, thereby contributing to an enhancement in maintenance property.
Moreover, the lid made of the light alloy by casting is small in size and simple in shape, as compared with the dispensing box body integral with the intake branch pipes and hence, can be precisely formed by casting such as high-pressure die-casting. Therefore, the post-processing of the valve bore is not required and moreover, the lid having a high rigidity and such a high quality that deformation cannot be generated therein even due to a change in the surrounding temperature, can be produced easily, and the good opening and closing operation of the on-off valve supported on the lid can be always ensured irrespective of the change in the surrounding temperature.
Moreover, the intake air inlet and the actuator are disposed at opposite ends of the intake air-dispensing box and hence, it is possible to avoid the interference of the valve shaft supporting the on-off valve and the intake air inlet with each other to provide a reduction in span of the valve shaft. Furthermore, since the bearing bores supporting the valve shaft are disposed in the offset manner as described above, they can be made easily and with a high accuracy by a relatively short drill.
According to a seventh aspect and feature of the present invention, in addition to the sixth feature, a plurality of the valve bores opened and closed by a plurality of the on-off valves and at least three bearing bores coaxially arranged with the valve bores interposed therebetween are made in the other half of the partition wall.
With the seventh feature, it is possible to simultaneously achieve the ensuring of a total wide opening area of the valve bores and the prevention of the flexure of the valve shaft.
According to an eighth aspect and feature of the present invention, in addition to the sixth or seventh feature, the other half of the partition wall is divided into a main partition other-half body and a partition piece so that the valve bore is divided along the bearing bores into halves, the partition piece being bolted to the main partition other-half body.
With the eighth feature, when the main partition other-half body and the partition piece of the partition wall are formed, the halves of the valve bore included respectively in the main partition other-half body and the partition piece can be die-formed simply, and after the casting, a troublesome processing for the valve bore is not required, leading to an enhancement in productivity.
According to a ninth aspect and feature of the present invention, in addition to the sixth feature, the intake air-dispensing box is disposed in a vertically longer shape between rearward-directed heads of the first and second banks of the engine for an outboard engine system with a crankshaft disposed vertically and a rear wall of an engine hood for the outboard engine system for covering the engine; the intake air inlet is provided in an upper end of the intake air-dispensing box; and the actuator is mounted at a lower end of the intake air-dispensing box.
With the ninth feature, in the outboard engine system, the intake system can be accommodated compactly in a narrow space between the first and second banks of the engine and the engine hood, while avoiding the interference of the intake air inlet and the actuator with each other.
According to a tenth aspect and feature of the present invention, there is provided an intake system for a multi-cylinder engine, in which an intake air inlet is provided in one end of an intake air-dispensing box disposed on one side of an engine having first and second banks so that it leads to an intake passage in a throttle body; the inside of the intake air-dispensing box is divided by a partition wall into first and second dispensing chambers communicating with the intake air inlet; an on-off valve capable of permitting the first and second dispensing chambers to be put into and out of communication with each other is mounted in the partition wall; and first and second intake branch pipes opening into the first and second dispensing chambers respectively and leading to intake ports in the first and second banks respectively are connected to the intake air-dispensing box; wherein the intake air-dispensing box is comprised of a dispensing box body which includes the intake air inlet, the first and second intake branch pipes and one of halves of the partition wall and which has an opening provided in its outer wall opposite from the first and second intake branch pipes to extend between the first and second dispensing chambers, and a lid which is made of a light alloy by casting and which has the other half of the partition wall and a loop-shaped surrounding wall integrally, projectingly provided on its inner surface and detachably coupled to an outer surface of the dispensing box body to surround the opening; a valve bore permitting the first and second dispensing chambers to be put into communication with each other and bearing bores supporting a valve shaft of the on-off valve for opening and closing the valve bore are provided in the other half; and an outward bulge is formed at a portion of the lid corresponding to the valve bore in order to enlarge the valve bore.
The first and second banks correspond to left and right banks 6L and 6R in the embodiment of the present invention which will be described hereinafter.
With the tenth feature, a single assembly is formed by the lid and the on-off valve and hence, the maintenance of the on-off valve and the members around the on-off valve can be carried out easily by removing the lid from the dispensing box body, thereby contributing to an enhancement in maintenance property.
Moreover, the lid made of the light alloy by casting can contribute to a reduction in weight of the intake air-dispensing box and maintain a predetermined shape without being influenced by a change in the surrounding temperature and moreover, is reinforced effectively by the surrounding wall on the inner surface. Therefore, the bearing bores for the valve shaft made in the other half of the partition wall integral with the lid cannot be deformed, whereby the stable operation of the on-off valve can be ensured. Further, the surrounding wall on the inner surface of the lid also serves to enlarge a runner during formation of the lid by casting to enhance the castability of the lid and hence, also contributes to an improvement in quality of the lid.
In addition, the outward bulge formed at the portion of the lid corresponding to the valve bore provides an increase in height of the other half of the partition wall at the bulge, whereby the valve bore having a large opening area can be formed, but also an increase in weight of the intake air-dispensing box can be provided by the outward bulge.
Particularly, the lid having the valve bore is small in size and simple in shape, as compared with the dispensing box body integral with the intake branch pipes and hence, can be precisely formed by casting such as high-pressure die-casting. Therefore, the post-processing of the valve bore is not required and moreover, the lid having a high rigidity and such a high quality that deformation cannot be generated therein even due to a change in the surrounding temperature, can be produced easily, and the good opening and closing operation of the on-off valve supported on the lid can be always ensured irrespective of the change in the surrounding temperature.
According to an eleventh aspect and feature of the present invention, in addition to the tenth feature, the bearing bores are made in the other half of the partition wall from an end opposite from the intake air inlet.
With the eleventh feature, the bearing bores can be made easily and with a high accuracy by a relatively short drill to contribute to the stabilization of the operation of the on-off valve irrespective of the existence of the intake air inlet.
According to a twelfth aspect and feature of the present invention, in addition to the tenth or eleventh feature, the other half of the partition wall is divided into a main partition other-half body and a partition piece so that the valve bore is divided along the bearing bores into halves, the partition piece being bolted to the main partition other-half body.
With the twelfth feature, when the main partition other-half body and the partition piece of the partition wall are produced by casting, the halves of the valve bore included respectively in the main partition other-half body and the partition piece can be die-formed simply, and a troublesome processing for the valve bore is not required after the casting, leading to an enhancement in productivity.
According to a thirteenth aspect and feature of the present invention, in addition to the first feature, the intake air-dispensing box is disposed in a vertically longer shape between rearward-directed heads of the first and second banks of the engine for an outboard engine system with a crankshaft disposed vertically and a rear wall of an engine hood for the outboard engine system for covering the engine; the intake air inlet is provided in an upper end of the intake air-dispensing box; and the actuator for driving the on-off valve is mounted at a lower end of the intake air-dispensing box through the valve shaft.
With the thirteenth feature, in the outboard engine system, the intake system can be accommodated compactly in a narrow space between the first and second banks of the engine and the engine hood, while avoiding the interference of the intake air inlet and the actuator with each other.
According to a fourteenth aspect and feature of the present invention, in addition to any of the first, third, sixth and tenth features, the bearing bore rotatably supporting the valve shaft of the on-off valve and an annular seal housing adjoining an outer end of such bearing bore are defined in the intake air-dispensing box, and a seal member is mounted in the seal housing and has first and second lips protruding outwards and inwards of the intake air-dispensing box respectively to come into close contact with an outer peripheral surface of the valve shaft.
With the fourteenth feature, when a negative suction pressure is applied to the intake air-dispensing box, the outward-directed first lip of the seal member receives the negative pressure to increase a sealing force on the valve shaft. In addition, when a positive pressure is applied to the intake air-dispensing box due to the pulsation of intake air or an air blowing-back phenomenon, the inward-directed second lip of the seal member receives the positive pressure to increase the sealing force on the valve shaft. Therefore, it is possible to prevent external dust from entering the intake air-dispensing box through the bearing bores for the valve shaft and to prevent a blow-by gas in the intake air-dispensing box or an oil contained in the blow-by gas from being leaked to the outside, by the single seal member. In addition, it is not necessary to particularly increase a force of resilient contact of the each lip itself of the seal member with the valve shaft and hence, the frictional resistance against the rotation of the valve shaft due to the seal member can be suppressed to the minimum, and it is possible to contribute to a reduction in capacity of the actuator for operating the on-off valve.
According to a fifteenth aspect and feature of the present invention, in addition to the fourteenth feature, the seal housing with the seal member mounted therein is defined in a lower end wall of the intake air-dispensing box through which the valve shaft disposed substantially vertically extends.
With the fifteenth feature, when a layout, in which the valve shaft disposed substantially vertically extends through the lower end wall of the intake air-dispensing box, is employed, even if the oil in the blow-by gas is accumulated on a bottom in the intake air-dispensing box, such oil can be prevented reliably by the first and second lips of the seal member from being leaked out of the intake air-dispensing box due to its own weight.
The above and other objects, features and advantages of the invention will become apparent from the following detailed description of the preferred embodiment taken in conjunction with the accompanying drawings.